Counterbalanced tiltable table



p 4, 1952 E. H. MAY ETAL 3,052,057

COUNTERBALANCED TILTABLE TABLE Filed Dec. 12, 1960 Unie This invention relates to improvements in drafting tables of the type having a tiltable drafting board.

An important object of this invention is to provide a drafting table having a tiltable top or drafting board and which has an improved arrangement for angularly adjusting the position of the board and for counterbalancing the board so as to facilitate the movement of the board between different angularly adjusted positions.

Another object of this invention is to provide a drafting table having a tiltable drafting board in which the counterbalance is adjustable for difierent boards and different accessories on the board.

Still another object of this invention is to provide a drafting table having a drafting board mounted for pivotal movement about an axis offset from the underside of the board in which the board and the drafting instruments on the board is counterbalanced when the board is tilted to either a horizontal or an upright position.

A more particular object of this invention is to provide a drafting table having a tiltable drafting board, an arcuate locking bar concentric with the pivot axis of the tiltable board, and lock means engageable with the bar for locking the board in different angularly adjusted positions, and which has a counterbalancing spring guidably disposed around the arcuate locking bar and arranged to counterbalance the drafting board.

These, together with various ancillary objects and advantages of this invention will be more readily appreciated at the same becomes better understood by reference to the following detailed description when taken in connection with the accompanying drawings wherein:

FIGURE 1 is a fragmentary side elevational view of the drafting board and illustrating the tiltable mounting and counter-balance for the board;

'FIG. 2 is a fragmentary sectional view of the apparatus for mounting and counterbalancing the tiltable drafting board taken on the lane 2-2 of FIG. 1.

The present application is a continuation-in-part of our copending application of Ellwood H. May and Victor J. Kritske for Counterbalanced Tiltable Table, Serial No. 28,976, filed May 13, 1960, now abandoned.

Reference is now made more specifically to FIG. 3 of the drawings wherein there is shown a drafting table including a base having a drafting board support post 11. The table adjusting mechanism is of the type disclosed and claimed in the co-pending application of Ellwood H. May for Adjustable Support for Drafting Table, Serial No. 767,713, filed October 13, 1958, now Patent No. 2,982,050, dated May 2, 1961. In general, the adjustable drafting board support includes a pair of vertically swingable arms 12 and 13 at each end of the base 10, and which arms are pivotally attached as indicated at 14 and 15 to the base for vertical swinging movement. The post 11 is pivotally attached by pins 16 and 17 to the outer ends of the arms to form a parallelogram type linkage therewith so that the post remain-s in an upright position as it is raised and lowered. A height counterbalance spring 18 is attached at one end 19 to the base and at the other end to a lateral projection 21 on the lower arm 13 to yieldably urge the post 11 and the drafting board carried thereby to an elevated position.

The drafting board 22 is attached to the upper end of the posts 11 in such a manner as to permit tilting of the table or drafting board. For this purpose, a pair of latatent erally extending support brackets or plates 23 are attached to the board 22 and extend laterally from the underside thereof. The brackets 23 are located relatively close to one side edge designated 22a of the drafting board to provide adequate knee room below the lower edge of the board in all operative positions of the latter. The brackets 23 are pivotally attached by pins 25 to the posts 11 at a point spaced below the upper ends of the posts, so that the board can be tilted relative to the posts about the horizontal axis of the pins.

A semi-circular locking bar 28 is attached to each of the posts and is disposed concentric with the axis of the pivot pins 25. As shown, the arcuate bars extend forwardly of the respective posts 11, at the side adjacent the lower edge 23 of the drafting board, and the upper end of each of the rods extends across the upper end of the respective post. A rearwardly extending bracket 29 is secured as by welding to the upper ends of each of the posts and has a socket 31 thereon for receiving the upper end of the arcuate bar 28. A set screw 32 is threaded into the socket and engages the bar to lock the same to the post. A screw or similar fastener 30 is provided for attaching the lower end of the arcuate bar to the post at a point below the pivot pin 25. A locking mechanism including a rock shaft is rotatably mounted in the support brackets 23 and has apertured locking plates 34 nonrotatably disposed in slots 33 in the rock shaft. The locking plates are retained in the slots 33a by pins 40. The arcuate bars 28 extend through the openings 34' in the locking plates 34 and a spring 35 is attached by a pin 36 to the rock shaft 33 to turn the same about its axis and thereby tilt the locking plates 34 about an axis transverse to the bar so that the locking plates normally grip the respective locking bar 28. A lever 39 is-attached to the bar to enable manual release of the locking mechanism. In this manner the table can be selectively locked in different angularly adjusted positions.

Since the pivot axis 25 of the drafting table is located relatively close to one side edge 22a than to the other side edge 22b thereof, it is apparent that the board will not be balanced as it moves toward a horizontal position. In the relatively large size drafting boards, this unbalance becomes appreciable and makes angular adjustment of the positioning of the table difficult. This condition is aggravated when accessories, such as a drafting machine indicated generally by the numeral 41, are mounted on the drafing board. Such machines are generally attached to the upper edge 22b of the drafing board and overbalance the board in a direction tending to urge it toward a horizontal position to the extent that considerable effort is required to adjust the-board. In accordance with the present invention, a counterbalance spring is provided for counterbalancing the drafting board and any machine thereon and is so arranged as to apply a progressively increasing counterbalance pressure to the [board as the board moves toward a horizontal position. The counterbalance spring 42 is of the coil type and is disposed around the arcuate bar 28 so as to be guided thereon. A generally L-shaped guide bracket 43 is attached to each of the support brackets 23 and each guide bracket has spaced furcations 44 in the horizontal leg thereof for loosely straddling the respective locking bar 28. A washer 45 is interposed between the furcations on the guide bracket and one end of the spring 42. A stopcollar 46 is slidably mounted on the upper end of the arcuate bar 28 and engages the other end of the spring 42. The stop collar 46 may be selectively locked in ad justed position by a set screw 47. As will be noted, the collar 46 can be adjusted along the bar 28 to control the compression of the spring 42 and hence the counterbalance force applied to the table. The guide bracket 43 is offset from a plane through the pivot axis 25 and normal to the drafting board in a direction toward the lower edge 22a of the drafting board, and the upper end of the stop bar 28 extends across the upper end of the post 11 so as to. provide clearance between the guide bracket 43 and the stop collar 46, when the drafting table is in a horizontal position, to thereby prevent bottoming of the spring. As the table moves toward a horizontal position, the spring is progressively compressed and applies a progressively greater force to the guide bracket 43 to counterbalance the overhang of the drafting table and any drafting machine thereon. 7 Since the spring is disposed around the guide bar 28, it is effectively guided thereby and, as will be noted from FIGURE 1, closely underlies the drafting table 22 so as to not obstruct the knee space below the drafting table.

As the drafting board moves away from a horizontal position and toward an upright position, the center of mass of the board and any instruments mounted thereon shifts to the right as viewed in FIG. 1 and at intermediate inclined position, hereinafter referred to as the balance position, the center of mass moves into vertical alignment with the pivot pin 25. Due to the overhang of the drafting board, and the weight of any drafting instruments such as 41 mounted on the rear end of the board, the board usually does not reach its balance position until the board is inclined at an angle somewhat greater than 45 to the horizontal. The length and strength of the spring 42 and the position of the collar 46 is preferably selected so that the spring 42 continues to press the board toward its upright position until the board reaches the aforementioned balance position. Since the pivot axis 25 of the board is offset an appreciable distance from the underside of the board, the board tends to swing downwardly as it moves from the balance position toward an upright position. In order to counterbalance the board as it moves toward an upright position, a second balancing spring 5-1 is provided on the arcuate bar 28. The spring 51 is located below the locking plate 34 and a collar 52 is slidably supported on the bar and locked in positiion by a set screw 53 to enable adjustment of the spring. The length and strength of the spring 51 is preferably selected to substantially counterbalance the table and the instruments thereon as the table moves past the balance position toward an upright position. In the form shown, the spring 52 is short as compared to the spring 42 and is arranged to engage the locking plate 34 only after the board has moved. past the balance position toward an upright position, to counterbalance the board under these conditions. The adjusting collar 52 is provided to compensate for the different weight of the board and any instruments and is movable upwardly along the bar 28 to increase the counterbalancing pressure of the spring.

We claim:

1. In a drafting table, the combination of a support, a drafting board, a pair of support brackets attached to said board adjacent opposite ends and extending transverse to the underside thereof, means pivotally attaching said brackets to said support for movement relative thereto about a horizontal axis offset below the underside of said board between a generally horizontal and a generally upright position, said pivot axis being located relatively closer to the side edge of said board which is lowermost when the board is in said upright position than to the other side edge thereof, an arcuate rod attached to said support alongside each of said brackets and disposed concentric with said pivot axis, locking means attached to said support brackets and engaging said arcuate bar for selectively locking the drafing board in a preselected tilted position, guide brackets attached to each support bracket and loosely receiving a respective one of said bars, a coil spring disposed around each bar and having one end thereof abutting a respective guide bracket to yieldably oppose movement of said, board toward said horizontal position with a force that increases as the board approaches said horizontal position, and stop means engaging the other end of the springs for compressing the same to yieldably urge the board in a direction to counterbalance the board.

2. In a drafting table, the combination of a support, a drafting board, a pair of support brackets attached to said board adjacent opposite ends and extending transverse to the underside thereof, means pivotally attaching said brackets to said support for movement relative thereto about a horizontal axis offset below the underside of said board between a generally horizontal and a generally upright position, said pivot axis being located relatively closer to the side edge of said board that is lowermost when the board is upright than to the other side edge thereof whereby the board is overbalanced as it approaches said horizontal position, the offset between said board and said pivot axis causing said board to be overbalanced as it approaches said upright position, an arcuate rod attached to said support alongside each of said brackets and disposed concentric with said pivot axis, locking means attached to said support brackets and engaging saidarcuate bar for selectively locking the drafting board in a preselected tilted position, first and second coil springs disposed around each bar at opposite sides of said looking means, said first and second springs having one end thereof engageable with the respective support bracket when the :board is respectively swung to a horizontal and to an upright position, and first and second step means engaging the other ends of said first and second springs for anchoring said other ends of the springs to said arcuate bar whereby said first and second springs are operative to counterbalance said board when it is respectively moved to a horizontal and to an upright position.

3. In a drafting table, the combination of a pair of support posts, means for mounting the posts on a base, a drafting board, a pair of support brackets attached to said board adjacent opposite ends and extending transverse to the underside thereof, means pivotally attaching said brackets to said support posts for movement about a horizontal axis laterally oifset below the underside of the board between a generally horizontal and a generally upright position, said pivot axis being located relatively closer to the side edge of the board that is lowermost when the board is upright than to the other side edge thereof whereby the board is overbalanced as it approaches said horizontal position, a pair of semi-circular bars each attached to a respective one of said posts and extending concentrically of said pivot axis at the side of said post adjacent said one edge of the board, a guide bracket attached to each support bracket and loosely receiving a respective one of said semi-circular bars, said guide brackets being offset from a plane through said pivot axis and normal to the board in a direction toward said one side edge of the board, locking means attached to said support brackets and engaging said semi-circular bars at a point angularly spaced from said guide brackets, a coil spring disposed around each of said semi-circular bars and engaging said guide brackets to yieldably oppose movement of said board toward said horizontal position with a force that increases as the board approaches said horizontal position to counterbalance the weight of the board, and a stop mounted on each semi-circular bar for adjustment therealong and engaging the other end of a respective one of the springs for adjusting the compression of the springs to accommodate different weights on the board.

4. The combination of claim 3 wherein the upper ends of said semi-circular bars extend across the upper ends of the respective posts, and means attaching the upper ends of the bars to the respective posts.

5. 'In a drafting table, the combination of a pair of support posts, means for mounting the posts on a base, a drafting board, a pair of spaced support brackets attached to said board and extending transverse to the underside thereof, means pivotally attaching said brackets to said support posts for pivotal movement about an axis offset below the underside of the board between a generally horizontal and a generally upright position, said pivot axis being located relatively closer to the side edge of said board which is lowermost when the board is in said upright position whereby the board is overbalanced as it approaches said horizontal position, said offset between the pivot axis and the underside of the board causing the board to be overbalanced as it approaches said upright position, a pair of semi-circular bars attached to a respective one of said posts and extending concentrically of said pivot axis, locking means mounted on said support brackets and engageable with said semi-circular bars intermediate the ends thereof for locking the board in a selectively angularly adjusted position, a first coil spring disposed around said semi-circular bar above said locking means for counterbalancing the board as it is moved toward a horizontal position, and a second coil spring disposed around said semi-ci-rcular bar below said locking means for counterbalancing said board when it is moved toward an upright position.

6. In a drafting table, the combination of a pair of posts, means mounting the posts on a base, a drafting board, a pair of spaced support brackets attached to said board and extending transverse to the underside thereof, means pivotally attaching said brackets to said support posts for pivotal movement about an axis offset below the underside of the board, a pair of semi-circular bars attached to a respective one of the posts and extending concentrically of said pivot axis, locking means mounted on said support brackets and engageable with said semicircular bars intermediate the ends thereof for locking the board in a selected angularly adjusted position, a first coil spring disposed around said semi-circular bar above said locking means for counterbalancing the board as it is moved toward a horizontal position, a second coil spring disposed around said semi-circular bar below said locking means for counterbalancing said board as it is moved toward an upright position, said first coil spring being longer than said second coil spring.

"7. In a drafting table, the combination of a pair of posts, means mounting the posts on a base, a drafting board, a pair of spaced support brackets attached to said board and extending transverse to the underside thereof, means pivotally attaching said brackets to said support posts for pivotal movement about an axis ofiset below the underside of the board, a pair of semi-circular bars attached to a respective one of the posts and extending concentrically of said pivot axis, locking means mounted on said support brackets and engageable with said semicircular bars intermediate the ends thereof for locking the board in a selected angularly adjusted position, a first coil spring disposed around said semi-circular bar above said locking means for counter-balancing the board as it is moved toward a horizontal position, a second coil spring disposed around said semi-circular bar below said locking means for counterbalancing said board as it is moved toward an upright position, first and second stops on each semi-circular bar respectively engaging the ends of said first and second coil springs remote from said locking means, and means for adjustably locking said stops to the respective semi-circular bar to adjust the counterbalance force applied by the springs.

8. In a drafting table, the combination of a pair of posts, means mounting the posts on a base, a drafting board, a pair of spaced support brackets attached to said board and extending transverse to the underside thereof, means pivotally attaching said brackets to said support posts for pivotal movement about an axis offset below the underside of the board, a pair of semi-circular bars attached to a respective one of the posts and extending concentrically of said pivot axis, locking means mounted on said support brackets and engageable with said semicircular bars intermediate the ends thereof for locking the board in a selected angularly adjusted position, a first coil spring disposed around said semi-circular bar above said locking means for counterbalancing the board as it is moved toward a horizontal position, a second coil spring disposed around said semi-circular bar below said locking means for counterbalancing said board as it is moved toward an upright position, and a guide bracket attached to each support bracket and loosely receiving a respective one of the circular bars above the locking means, said first coil spring engaging said guide bracket.

9. In a drafting table, the combination of a support post, a drafting board, a support bracket attached to said board and extending transverse to the underside thereof, means pivotally mounting the bracket on said support post for movement about a horizontal axis laterally offset below the underside of the board between a generally horizontal and a generally upright position, said pivot axis being located relatively closer to the side edge of the board that is lowermost when the board is upright than to the other side edge thereof whereby the board is overbalanced as it approaches said horizontal position, a semi-circular bar attached to said post and extending concentric to said pivot axis, said semi-circular bar extending from a point on said post below said pivot axis upwardly at one side of the post and having a portion at its upper end extending crosswise of the post adjacent the upper end of the post and terminating at the other side of the post, means movable with said board and engaging said semi-circular bar for selectively locking said board in a preselected angularly adjusted position, a coil spring disposed around said bar above said locking means, and stop means on said portion of said bar engaging one end of said spring whereby said spring is operative to yieldably oppose movement of said drafting board in one direction toward said horizontal position with a force that increases as the board approaches said horizontal position to counterbalance the board.

References Cited in the file of this patent UNITED STATES PATENTS 2,356,924 Froelich Aug. 29, 1944- 2,461,627 Brewster Feb. 15, 1949 2,699,367 Lipphaus et a1. Jan. 11, 1955 

